The present invention relates to a stapler and more particularly, to a stapler having a handle plate which needs no heat treatment and having a feature of maintaining a minimum effective width of a slot for staple passing thereby.
A conventional stapler shown in FIG. 1 and 2 includes a base 80, a pusher 50, a main plate 40, a handle plate 70 and a handle 81. The base 80 has two lugs 82 extending upward from an upper surface of an end thereof for pivotal engagement to the handle 81, the handle plate 70 and the pusher 50 therebetween by a rivet 83. A spring 801 is disposed between the base 80 and the pusher 50. The pusher 50 having a U-shaped cross-section has first and second ends, a front wall 54 is formed at the first end thereof, an opening 541 is defined beside the front wall 54 in a bottom of the pusher 50, and two first catches 51 and a stop 52 extend upward from the bottom thereof. The main plate 40 has first and second ends, two flanges 42 extending downward from both sides thereof and is received in the pusher 50 so as to define a slot 55 between the front wall 54 of the pusher 50 and the first end of the main plate 40 to allow staples to be ejected therethrough. Two second catches 41 corresponding to the first catches 51 extend downward from an under side of the main plate 40, a first spring 53 is disposed between the main plate 40 and the pusher 50 and is restrained between the stop 52 and the second catch 41 such that the slot 55 is adjusted when a staple with larger cross-section passes therethrough by pushing the main plate 40 away from the front wall 54.
The handle plate 70 has first and second ends, the first end thereof has a protrusion 71 projecting therefrom and the handle plate has a second spring 72 disposed between an under side of the handle 81 and the handle plate 70, an ejector 61 has an opening 62 for the protrusion 71 to pass therethrough and its upper end is fixed to the under side of the handle 81 such that the handle plate 70 exerts a downward force to the ejector 61 to keep the ejector 61 maintaining a certain position which ensures the ejector 61 passes through the slot 55 precisely. When a user pushes the handle 81 downward, both the ejector 61 and the handle plate 70 will be push downward to the pusher 50, the handle 81 will press the second spring 72 when the handle plate 70 is stopped by contacting the main plate 40 such that the ejector 61 is pushed continuously into the slot 55 and pushes a staple mounted on the main plate 40 through the slot 55 on an object to be stapled, such as several sheets of paper.
However, the handle plate 70 needs a heat treatment process to harden it and this results in a size change which increases a possibility of the protrusion 71 disengaging from the opening 62 of the ejector 61, and this reduces an accuracy of the ejector 61 passing through the slot 55. Further, the main plate 40 engages to the pusher 50 by an engagement of the first and second catches 51 and 41 and by which the width of the slot 55 is maintained, but wear will occur between the first and second catches 41 and 51 after use for a period of time, namely, the slot 55 may be not wide enough to allow the staple to pass through. Furthermore, the handle 81, the handle plate 70, the pusher 50 and the base 80 are riveted together by the rivet 83, which means all the elements are riveted as one piece and cannot be exchanged if any one of them needs to be.
The present invention intends to provide a stapler having an improved structure to mitigate and/or obviate the above-mentioned problems.